Astrophysics > Solar and Stellar Astrophysics

Title:A tidally destructed massive planet as the progenitor of the two light planets around the sdB star KIC 05807616

Abstract: We propose that the two newly detected Earth-size planets around the hot B
subdwarf star KIC 05807616 are remnant of the tidally destructed metallic core
of a massive planet. A single massive gas-giant planet was spiralling-in inside
the envelope of the red giant branch star progenitor of the extreme horizontal
branch (EHB) star KIC 05807616. The released gravitational energy unbound most
of the stellar envelope, turning it into an EHB star. The massive planet
reached the tidal destruction radius of ~Ro from the core, where the planet's
gaseous envelope was tidally removed. In our scenario the metallic core of the
massive planet was tidally destructed into several Earth-like bodies
immediately after the gaseous envelope of the planet was removed. Two, and
possibly more, Earth-size fragments survived at orbital separations of >Ro
within the gaseous disk. The bodies interact with the disk and among themselves
and migrated to reach orbits close to a 3:2 resonance. These observed planets
can have a planetary magnetic field about ten times as strong as that of Earth.
This strong magnetic field can substantially reduce the evaporation rate from
the planets and explain their survivability against the strong UV radiation of
the EHB star.